Method for operating a field device

ABSTRACT

Method for operating a field device of process automation technology, wherein the field device is connected for communication with at least one servicing tool. In the case of a request by a servicing tool for access to the field device, the access allowed by the field device depends on the particular servicing tool which places the access request, and on the operating state, in which the field device is located.

TECHNICAL FIELD

The present invention relates to a method for operating a field deviceof process automation technology, as well as to a field device ofprocess automation technology.

BACKGROUND DISCUSSION

In process automation technology, field devices are often employed,which serve to register and/or influence process variables. Serving forregistering process variables are sensors, such as, for example,fill-level measuring devices, flow measuring devices, pressure andtemperature measuring devices, pH-redox potential measuring devices,electrical conductivity measuring devices, etc., which register therespective process variables, fill-level, flow, pressure, temperature,pH-value and conductivity. Serving for influencing process variables areactuators, for example valves or pumps, via which the flow of a fluid ina section of pipeline or the fill-level in a container can be changed.In principle, all devices which are employed near the process and whichdeliver or work with process-relevant information are referred to asfield devices. In addition to the aforementioned sensors and actuators,generally, units that are directly connected to a fieldbus and whichserve to communicate with the superordinated units (e.g. remote I/Os,gateways, linking devices, etc.) are also referred to as field devices.A large number of these devices are produced and sold by theEndress+Hauser Group.

In modern industrial facilities, field devices are, as a rule, connectedwith superordinated units via fieldbus systems. Normally, thesuperordinated units involve control systems or control units, forexample a PLC (programmable logic controller) or a DCS (DistributedControl System). The superordinated units are used, among other things,for process control, process visualizing, process monitoring as well asin the start-up of the field devices. One or more of such superordinatedunits can, in such case, be directly connected to the fieldbus, to whichthe field devices are connected, and/or be connected to a superordinatedcommunication network.

In a field device, a plurality of parameters are provided. Parameters ofa field device include, for example, a measuring range, limit values,units, etc. By writing and reading the parameters of a fielddevice—which is also referred to as configuring (or parametering) thefield device—the functionality of the field device can, in each case, beadapted corresponding to the intended use. The configuring of a fielddevice is, as a rule, performed during the start-up of the field device.To the extent that changes should be performed during operation, aconfiguration can also partially occur during operation. A changing,activating and/or deactivating of parameters of a field device occurs,in such case, by a write accessing of the parameters. By a readaccessing, parameters of the field device can be read out; a change inthe parameters does not, in such case, occur.

For accessing parameters of field devices—especially for reading andwriting parameters of field devices—servicing programs, which are alsoreferred to as servicing, or operating, tools, are provided. Suchservicing tools can, in such case, be implemented on the field deviceitself, on a superordinated unit and/or on a servicing device, such as,for example, a portable personal computer (laptop), a portable handheldservicing device (handheld), a PDA (Personnel Digital Assistant), etc.An accessing of parameters of a field device via the servicing toolscan, in such case, occur automatedly, in the context of an application,or manually, by a user. As a rule, servicing tools make available to auser (who would like access to parameters of a field device) acorresponding user interface. A communication connection between aservicing device (e.g. a personal computer, portable handheld servicingdevice or PDA) and the field device is produced either via the fieldbus,to which the field device in question is connected, or directly via acorresponding service interface of the field device. A servicing toolwhich is implemented on the field device itself enables a user to accessthe field device on-site. In addition to providing access to fielddevices as explained, servicing tools can also have still otherfunctions.

Until now, access rights are statically defined in a field device, whichmeans, especially, that once set, or defined, access rights toparameters of the field device remain unchanged over time (assuming theyare not changed again). During the start-up of a field device, aparameter change is relatively non-critical, since such a change doesnot directly affect the process of a plant. In some operating states ofa field device, however, parameter changes are to be conducted only as amatter of exception and with high care, especially in an operating statein which the field device is integrated into the process of a plant, andchanges to the parameters settings can directly affect the process(operating state: on control). In this case, a parameter change which isincorrect or which is undergone at an incorrect point in time can havean unforeseeable effect on the process. A static definition of accessrights thus has the disadvantage, that in some situations, in whichparameter changes are relatively non-critical, more extensive accessrights are desirable; whereas in other situations, in which parameterchanges are critical, the defined access rights are possibly tooextensive.

In a plant of process automation technology, a field device is, as arule, connected for communication not only with one, but rather with aplurality of servicing tools. In such case, a coordination of accessingsby the different servicing tools often does not occur. This can lead totwo servicing tools accessing parameters of a field devicesimultaneously, or at such short time intervals, that an unpredictablebehavior and/or an error occurs in the current application. For example,it can occur that a first servicing tool accesses the field device, andloads all or a part of the parameters of the field device into theassociated processor unit, on which the servicing tool is implemented.These data are then available as offline data, which means that a changeof the same data (in the processor unit) does not directly affect theassociated parameters in the field device. The parameters are then, forexample, changed offline by way of the servicing tool, and then loadedback into the field device. After this loading, the changed parametersthen exist as online data in the field device. If, in parallel—that is,at the same time or overlapping in time—to the parameter change via thefirst servicing tool, another parameter change is also performed in thefield device via a second servicing tool, it can then occur that theparameter change of the first or the second servicing tool isunintentionally overwritten, or that the parameter change of the firstservicing tool is not compatible with the parameter change of the secondservicing tool. This can lead to unpredictable behavior in the process,or to the occurrence of errors.

Until now, existing measures have not been sufficient to reliably avoidthe above-mentioned causes for possible error. In known servicing tools,an identification method, by which users must first identify themselves(for example, through a password or through biometric data) is, as arule, provided. Depending on the type of task and the technicalknowledge of the relevant person, predetermined accesses are enabled viathe servicing tool. In this way, for individual persons, only suchaccesses are enabled for which, in each case, these persons areauthorized. This mechanism does not prevent, however, that two or morepersons access in parallel the same field device via different servicingtools. Additionally, this mechanism cannot prevent that a userunintentionally changes parameters of a field device which is currentlyin the operating state “on control”, and that errors in the process arecaused thereby.

Additionally, the use of so-called hardware-switches in field devices isalso known. Such involves, for example, mechanical switches, which areplaced directly on the field device, and whose actuation leads to thefield device being blocked from parameter changes of any type.Disadvantageous in such case, is, however, the fact that, in order toboth block parameter changes as well as for canceling this blocking, thefield device in question must, in each case, be located on-site, and therelevant switches must be actuated. Additionally, such a switch cannoteffectively and reliably eliminate the causes for error set forth above.

SUMMARY OF THE INVENTION

On the basis of these considerations, an object of the present inventionis to provide a method and a field device by which errors, which canoccur when accessing the field device, are more effectively prevented.

In the present invention, a method is provided for operating—especiallyfor configuring—a field device of process automation technology, thisfield device being connected in communication with at least oneservicing tool. In the case of a request by a servicing tool for accessto the field device, the access allowed by the field device depends, insuch case, on the particular servicing tool placing the access request,and on the operating state, in which the field device is located.

In comparison to the static definition of access rights in the state ofthe art (which is explained above), in the present invention, it istaken into consideration, among other things, in which operating statethe field device is located. In this way, it can especially be provided,that in operating states, in which an accessing (especially involvingparameter changes) is comparatively non-critical, more extensiveaccessings (or access rights) of the field device are defined than inoperating states, in which an accessing (especially involving parameterchanges) is comparatively critical, because, for example, theseaccessings directly affect the process of a plant. Various possibleoperating states of a field device are explained below.

Additionally taken into consideration in the present invention is fromwhich servicing tool an access request is placed. In this way, forexample, during the definition or setting of the accesses (or accessrights) to be allowed, one or more of the following criteria are, ineach case, specifically taken into consideration: The functions, whichthe relevant servicing tool provides with regard to an accessing of thefield device (especially with regard to an accessing of parameters ofthe field device); the control functions or control tasks, which theservicing tool performs within the plant; the hardware, on which theservicing tool is implemented; as well as the communication connection,via which the servicing tool communicates with the field device. On thebasis of these considerations, the access rights for different servicingtools can, in the present invention, differ from one another. As isexplained below in more detail, through the present invention, aparallel (that is a simultaneous or overlapping in time) accessing ofthe field device by a plurality of servicing tools can be prevented.Through this specific and situation-dependent allowing of access, theoccurrence of errors in the case of an accessing of the field device byat least one servicing tool can be more effectively prevented.

Preferably, it is provided that the field device is connected forcommunication with a plurality of servicing tools, wherein the accessallowed by the field device differs in the case of at least two of theservicing tools.

In the present context, the term, “servicing tool”, refers generally toa program, or tool, with which an accessing of field devices—especiallyan accessing of parameters of field devices—can be performed. In thepresent context, it is, in such case, unimportant, in which type ofhardware the servicing tool is implemented. As is explained above, theservicing tool can, for example, be implemented in the field deviceitself, in a superordinated unit and/or in a servicing device, such as,for example, a portable personal computer (laptop), a portable handheldservicing device (handheld), a PDA, etc. In such case, a number ofdifferent servicing tools can, in each case, be implemented ondifferent—or, alternatively, on the same—hardware, such as, for example,a personal computer or a computer unit. Through a servicing tool,especially the reading and writing (changing, activating and/ordeactivating) of parameters of the field device can be performed. Alongwith this, a servicing tool can also have still other functions.Especially, the individual servicing tools, which communicate with thefield device, can differ in the functions which are provided by them.

The communication connection between the servicing tool and the fielddevice can be implemented in different ways. It can, for example, occurvia a fieldbus (hardwired or wireless). This is, for example, the case,when the servicing tool is implemented on a portable personal computeror a PDA, which is connected to the fieldbus of the field device via acorresponding interface. Alternatively, the communication connection canbe formed via a service interface of the field device, to which acorresponding servicing device—such as, for example, a portable handheldservicing device—is connected. If the servicing tool is implemented on acomputer unit, this computer unit can then also be connected to asuperordinated network, and, via this network (and the fieldbus), it cancommunicate with the field device. Additionally, the communicationconnection can extend within the field device. Via a servicing toolimplemented on the field device, a person can, by operating a displayand service unit of the field device, have access to the field device,and especially display, change, activate and/or deactivate parameters ofthis same field device. As a rule, fewer functions are provided by aservicing tool which is implemented in the field device itself than, forexample, by a servicing tool which is implemented in a computer unit ora personal computer.

An “accessing” includes at least one accessing of parameters of thefield device, which especially includes the writing (activating,deactivating and/or changing) and/or reading of parameters of the fielddevice. Such parameters of the field device can especially concern“audit-trail” data, by which the chronological course of parameterchanges is documented, engineering data and/or process data.

Engineering data especially includes field device configuration,fieldbus configuration and/or configuration of an application.Parameters, which concern process data, can be, especially, units of theissued, measured values, status and diagnostic information, alarm anderror reports, etc.

The access allowed by the field device can, depending on the servicingtool which places the access request and depending on the operatingstate of the field device, be embodied in different ways. For example,in some situations (that is, particular servicing tools or particularoperating states of the field device), all accessing of the field devicecan be blocked, while in other situations, a limited accessing isallowed. The allowed accessing can also additionally be dependent onother conditions.

In an advantageous further development, it is provided that, dependingon the servicing tool which places the access request and/or dependingon the operating state of the field device, the access allowed by thefield device includes only a part of the parameters of the field device.In this way, differences in the individual parameters can also be takeninto consideration. As is explained above, there exist, for example,parameters (in the following: “critical parameters”) in the fielddevice, whose being changed directly affects the process of the plant.These “critical parameters” can, for example, be parameters of afunction block (for example, “scaling parameters”, “channel parameters”,etc.), which is implemented in the field device and integrated into theprocess. Additionally, they can be parameters, which concern units orlimit values of issued, measured values, and/or, if the field devicecommunicates via a fieldbus, parameters which relate to the busconfiguration. An accessing of critical parameters can, for example, inthe operating state “on control”, be completely blocked or onlypermitted for qualified personnel, while an accessing of otherparameters of the field device, whose being changed does not affect theprocess, is allowed. Such non-critical parameters can, for example, beparameters of the field device which relate to a field device functionblock, which is not integrated into the process, to the extent thatthese parameters do not concern the activation or integrating of thefunction block.

Additionally or alternatively, it can be provided that an accessing ofsome parameters of the field device is only allowed, when the relevantservicing tool fulfills one or more of the criteria regarding servicingtools which are listed above for claim 1, whereas an accessing of otherparameters is allowed independent of the fulfillment of such criteria.In some situations (i.e., particular servicing tools or particularoperating states of the field device), another option is to block anaccessing of all parameters of the field device.

In an advantageous further development, it is additionally providedthat, depending on the servicing tool that places the access requestand/or depending on the operating state of the field device, the accessallowed by the field device includes only certain types of access. Theterminology, “types of access”, includes, especially, a read access anda write access of parameters of the field device. Write accessespecially includes the activation, deactivation and/or changing of oneor more parameters. In such case, for example, in the operating state“on control”, write access can be completely blocked, while read accessis still allowed. Additionally or alternatively, it can, for example, beprovided, that write access by a servicing tool of parameters of thefield device is only allowed, when the relevant servicing tool fulfillsone or more of the criteria regarding servicing tools which are listedabove for claim 1, whereas read access to parameters of the field deviceis allowed independently of the fulfillment such criteria.

Preferably provided in this further development is the allowance ofspecific access types combined with the further development explainedabove, which relates to the allowance of access to only a part of theparameters of the field device. For example, in the operating state “oncontrol”, only read access can be allowed to critical parameters, whilewrite access is also allowed to other (non-critical) parameters.

In an advantageous further development, it is provided that, when anaccess request is made, the at least one servicing tool transmits anidentification of the servicing tool to the field device. On the basisof this identification, the field device can detect which servicingtool—especially which type of servicing tool—is placing the accessrequest. The field device, as a function of this identification and as afunction of the operating state in which the field device is running,then allows an accessing. In the case of fieldbus systems, during theplacing of an access request, the identification of the sender—that isthe servicing tool—is, as a rule, transmitted (this is generally asreferred to as an identification procedure), so that a simpleimplementation of the method of the invention is thereby enabled.

It can, in such case, be provided, for example, that, for eachidentification, the corresponding accesses which are, in each case, tobe allowed for the different operating states of the field device (and,in given cases, for other criteria to be considered) are defined in thefield device. Such an association can, in such case, for example, occurtabularly. Alternatively, this association can also occur on the basisof predetermined algorithms, which are implemented in the field device.

In an advantageous further development, it is provided that profileinformation is stored for the at least one servicing tool in the fielddevice, wherein the profile information contains information regardingthe functions of the relevant servicing tool with regard to an accessingof field devices, and that the field device, upon obtaining an accessrequest by a servicing tool, accesses the profile information of thisservicing tool, and, as a function of this profile information, allowsan accessing by the servicing tool. This further development has theadvantage, that such profile information can be provided from amanufacturer of the servicing tool. The user of the servicing tool mustthen only load the profile information into the field device. If anaccess request is placed from a servicing tool, it can then bedetermined in the field device as a function of the associated profileinformation and on the basis of predetermined criteria, which accessesare allowed in which operating states of the field device. Thisdetermining can occur in the field device through a tabular associationof the accesses to be allowed with the respective profile informationand operating states, or on the basis of predetermined algorithms, whichare implemented in the field device, and which are to be applied to therespective profile information and operating states. This furtherdevelopment accordingly enables, that, in the field device, generictabular associations or algorithms are defined, on the basis of whichcan be ascertained which accesses, in each case, are to be allowed fordifferent servicing tools. If a unified form for representation of theprofile information is selected to be independent of manufacturer, theintegration of servicing tools from various manufacturers into themethod of the invention is then enabled in simple manner.

The profile information can include other information, in addition toinformation regarding the functions of the relevant servicing tool withregard to an accessing of field devices. Preferably associated with theprofile information are, in each case, identifications of the associatedservicing tools. In this way, the field device, in the case of obtainingan access request with the identification of the relevant servicingtool, can, on the basis of the identification, assign the associatedprofile information.

Profile information for servicing tools can, for example, be givenaccording to the document “Foundation® Fieldbus Host InteroperabilitySupport Test Profile and Procedures; document FF-569; 16 May 2007;revision: FS 2.0” (referred to in the following as “FF-document”) oraccording to subsequent revisions of this FF-document. Defined in theFF-document are, among other things, properties, which can beimplemented in a servicing tool (also referred to as “host”).Additionally, associated tests for these properties are given in theFF-document. It may only be claimed that a servicing tool exhibits aproperty defined in the FF-document when it has passed the associatedtests. Through the individual tests, it is especially checked whetherthe relevant servicing tool fulfills interoperability requirements inthe case of interaction with other servicing tools and field devices.Additionally provided in the FF-document are various profile classes(“host profile classes”), into which servicing tools are divided,according to their properties. Profile information according to thisFF-document is, as a rule, provided by the manufacturers of servicingtools, so such information need not be separately created. Recourse tothis profile information is advantageous, since this profile informationis applicable independently of manufacturer and has been verified bytests according to the FF-document. To the extent that correspondingprofile information is (or is to be) defined in other bus systems (suchas, for example, Profibus®, HART®, etc.), these can be used in acorresponding manner.

In an advantageous further development, it is provided that, in the caseof obtaining an access request from a servicing tool, an accessing byother servicing tools is blocked in the field device or enabled only tolimited extent. In this way, it is prevented that errors occur in thefield device due to parallel (that is simultaneous or overlapping intime) accessing by different servicing tools. Also preferable is that,in the case of an access request being placed, an identification of therelevant servicing tool is, in each case, transmitted by the differentservicing tools. In addition to blocking all access, allowing onlylimited access is also possible. A limited accessing, for example, canbe limited to certain access types (such as, for example, read access),or it can be limited to a part of the parameters of the field device.

Preferably, this further development is implemented in such a manner,that a further operating state, in which an accessing by other servicingtools is blocked or enabled only to a limited degree, is provided in thefield device. In the case of obtaining an access request from aservicing tool, the field device is switched into this additionaloperating state.

In an advantageous further development, it is provided that the blockingor limitation of access to the field device can only be canceled by theservicing tool which has placed that access request, due to which theaccessing was blocked or limited. In this way, it is assured thataccessing of individual servicing tools can, in each case, be executedin entirety, without this procedure being disturbed by other servicingtools. Thereby, it can additionally be prevented that two or moreaccesses, in the case of which the danger exists that they mutuallyinfluence or disturb each other, overlap in time. Preferably, theservicing tool also transmits its identification together with thereport that a blocking or limitation is to be canceled. As a rule, afterexecution of the access procedure, the “session” with the field deviceis ended by the servicing tool. In such case, it can be provided that,in the case of the session being terminated by the servicing tool, theblocking or limitation of access is also simultaneously canceled in thefield device.

In an advantageous further development, it is provided that the fielddevice, in the case of receiving an access request from a predeterminedservicing tool, allows an accessing by this predetermined servicing toolindependently of whether an access request was parallelly placed byanother servicing tool. In this way, it can, for example, be assured,that certain parameter settings which are important for the runningprocess can be performed by a predetermined servicing tool without a (orwith only a small) time delay. Such important parameters settings can,for example, concern application-related parameters, such as units ofmeasured values, limit values of measured values and/or linkinformation, etc. In such case, a number of predetermined servicingtools can also be used parallely in a plant.

Preferably, in such case, it is provided that, when an access request isreceived by the predetermined servicing tool, an (in given cases, justprocessed) access request by another servicing tool is prematurelyended. It can additionally be provided that a just processed accessrequest by another servicing tool is only ended prematurely, when thepredetermined servicing tool transmits, together with the accessrequest, a report stating that the access request is urgent orimportant. Such an early termination can be implemented, for example, insuch a manner, that the original parameter settings are maintained, andsuch other servicing tool must repeat the access request at a laterpoint in time.

In an advantageous further development, it is provided that, when anaccessing is blocked or enabled only to a limited degree, the fielddevice gives a corresponding notification concerning the blocking orlimitation. Preferably, in the notification, an identification is givenof the servicing tool, which has placed the access request due to whichthe accessing was blocked or limited. The notification can be given, forexample, on a display of the field device. Additionally, it can beprovided that, when another servicing tool places a request for accessto the field device, the field device transmits to this other servicingtool (e.g. via a fieldbus or a service interface) with the notificationa report regarding the blocking or limitation. Giving such anotification has the advantage that a user or an application is directlyinformed that an accessing is not possible or is only possible to alimited degree at the particular point in time. Additionally, stillother information—such as, for example, the probable duration of theaccess—can also be given in the notification.

In an advantageous further development, it is provided that, includedamong those operating states of the field device, as a function of whichan accessing is allowed, is at least one of the following operatingstates: An “offline” operating state, in which the field device is notconnected in a plant of process automation technology; an “online”operating state, in which the field device is connected in a plant ofprocess automation technology; a “commission” operating state(“start-up” operating state), in which parameters of the field deviceare set before integration of the field device into a process; a“non-commission” operating state (operating state before start-up), inwhich a field device, which has not previously been in operation, ispresent; a “off-control” operating state, in which the field device is“online”, but is, however, not yet integrated into a process; an“on-control” operating state, in which the field device is “online” andintegrated into a process; and an operating state in which access isblocked or limited, in which the field device is operated, when arequest for access to the field device is placed by a servicing tool.

“Connected in a plant of process automation technology” means here thatthe field device is connected in the plant as regards its hardware. Inthe case of a hardwired connection of the field device, this means, forexample, that the field device is connected by cable. During the“commission” operating state, among other things, parameters of thefield device are set (for example, via a corresponding servicing tool)so that the field device can then fulfill the desired functionality inan “on-control” operating state. During the “commission” operatingstate, the field device can be either “online” or “offline”. In thepresent context, “integrated into a process” means that the field deviceactually interacts with the process (of a plant of process automationtechnology), which means that its control loops are integrated into theprocess. In the case of the field device being a sensor, this can, forexample, include registering measured values and transmitting these toother plant devices, in which the measured values are to be made use of.In the case of the field device being an actuator, the interaction withthe process can include acting on the process, such as, for example,changing an amount of flow in a section of pipeline as a function ofreceived control signals. As can be seen from the explanations, a fielddevice can also be parallelly operated in several of the operatingstates set forth above.

In an advantageous further development, it is provided that, in the caseof an access request which is initiated by a person, this person mustidentify him/herself, and the access allowed by the field device dependson the identity of this person. It can, for example, in such case beprovided, that the person must identify him or herself through biometricdata (such as, for example, a finger print), or with a password. In thefield device—or also in the servicing tool—access rights can be definedfor different persons or groups of persons in a predetermined manner.The accessing allowed by the field device then occurs only within thecontext of these predetermined access rights. By additionally takinginto consideration the identity the person, by whom an access request isinitiated, an unauthorized accessing by a non-authorized person isprevented.

The present invention additionally relates to a field device of processautomation technology, wherein the field device includes a processorunit. The processor unit is, in such case, adapted in such a manner,that, in the case of a request by a servicing tool for access to thefield device, the access to the field device allowed by the processorunit depends on the particular servicing tool which places the accessrequest, and on the operating state, in which the field device isrunning. The terminology, “processor unit”, means, in general, a dataprocessing unit (such as, for example, a CPU, a microprocessor, etc.).The advantages, variants and further developments of the method of theinvention explained above are also implementable in corresponding mannerin the system of the invention.

The functionality implemented in the field device, as well as thecorresponding interaction between servicing tool and field device, whichare provided in the present invention and/or in one of the furtherdevelopments, can, for example, be described in a device description(DD) of the field device. The device description is, as a rule, createdin a text-based form (e.g. in the ASCII-text format). For this purpose,depending on the fieldbus system used, different device descriptionlanguages are used, such as, for example, the HART® Device DescriptionLanguage, Foundation Fieldbus Device Description Language, ElectronicDevice Description Language (EDDL), Field Device Configuration MarkupLanguage and GSD/Profibus® (GSD: General Station Description). In orderthat a servicing tool can access the information contained in the devicedescription, an interpreter is, as a rule, provided, through which theinformation provided in the device description is interpreted ortranslated, and supplied to the servicing tool.

Alternatively, the functionality implemented in the field device—as wellas the corresponding interaction between the servicing tool and fielddevice, as provided in the present invention and/or in one of thefurther developments—can be described and implemented in a device driverof the field device, especially in a “Device Type Manager” (DTM). Adevice driver—especially a “Device Type Manager”—is, in such case,device-specific software, which encapsulates data and functions of thefield device and provides graphical servicing elements. A servicing toolmust, in this case, be embodied in such a manner, that it forms asuitable frame application for the device driver. For example, a “DeviceType Manager” requires a FDT frame application (FDT: Field Device Tool)in order to run. One servicing tool which forms such a FDT-frameapplication is, for example, the “FieldCare®” application ofEndress+Hauser.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages and utilities of the invention will become evident onthe basis of the appended drawing, the sole FIGURE of which shows asfollows:

FIG. 1 is a schematic representation of a fieldbus network for purposesof explaining a form of embodiment of the present invention.

DETAILED DISCUSSION IN CONJUNCTION WITH THE DRAWING

In the representation in FIG. 1, three field devices F1, F2 and F3, aswell as a programmable logic controller PLC, are connected to a fieldbusF. The fieldbus F works according to the Profibus® standard. The controlunit PLC is a master, while the field devices F1, F2 and F3 are slaves.Communication between the control unit PLC and the field devices F1, F2and F3 occurs according to the Profibus® standard. The fieldbus F isconnected via a gateway G to a superordinated network N. In addition tothe fieldbus F, other fieldbusses (not shown) can also be connected withthe superordinated network N. Connected to the superordinated network Nis a first personal computer 2, on which a first servicing tool isimplemented. Connected to the superordinated network N is furthermore asecond personal computer 4, on which a second servicing tool isimplemented. In the situation presented in FIG. 1, the field device F3is sought out by a person in the form of a service technician 6, whocarries a handheld servicing device 8. On the handheld servicing device8, a third servicing tool is implemented, through which the reading andwriting of parameters of the field device F3 is enabled. For this, thehandheld servicing device 8 (as it is presented in FIG. 1) is connectedto a service interface 10 of the field device F3.

In the present example of an embodiment, it is provided, that the firstservicing tool primarily performs tasks of process control, both openand closed loop. In such case, the first servicing tool monitorsmeasured values, as well as status and diagnostic information in theplant. Additionally, the first servicing tool has visualizing andmonitoring systems. Such a servicing tool is provided by the firmEndress+Hauser, for example, in the form of the servicing tool,“FieldControl®”. Additionally, it is provided that the first servicingtool performs the configuration of an application, which especiallyincludes combining individual function blocks of field devices in such amanner, that a desired application is thereby implemented. Software,with which such a configuration of an application is put into practice,is provided by the firm, Endress+Hauser, for example, in the form of theservicing tool “Application Designer®”.

Assumed by the second servicing tool are primarily tasks of plant assetmanagement. Such a servicing tool is provided by the firmEndress+Hauser, for example, in the form of the servicing, or operating,tool “FieldCare®. Along with this, parameters of the individual fielddevices can also be read and written via the second servicing tool.

An accessing of the field devices of the plant, and especially of thefield devices F1, F2 and F3 can, thus, occur both from the first as wellas from the second servicing tool. An accessing especially includes, insuch case, the writing and reading of parameters of the relevant fielddevices. Additionally, with the third servicing tool (which isimplemented on the handheld servicing device 8), the field device F3 canbe accessed. Additionally, the field device F3 can also be accessed viaa fourth servicing tool which is implemented on the field device F3itself; wherein, for this purpose, a person must operate a display andservice unit (not shown) of the field device F3.

In the following, an example of the procedure of the method of theinvention will now be explained. The first servicing tool sends to thefield device F3 a write request for a parameter of the field device F3.Together with the write request, the servicing tool transmits itsidentification. Upon receiving the write request, all write access forother servicing tools is blocked in the field device F3. The fielddevice F3 has stored in a memory, profile information for the differentservicing tools in the plant. Associated with the profile informationis, in each case, an identification of the corresponding servicing tool.The identifications of the different servicing tools are, in each case,granted only uniquely within the plant. The field device F3 can thusaccess the associated profile information via the receivedidentification. As a function of the profile information, and also as afunction of the operating state in which the field device F3 is running,access rights are defined in the field device F3. The field device is,at this moment, running in an “on-control” operating state. The relevantparameter of the field device to be changed through the received writerequest is not critical for the current application, which means achange of the same does not directly affect the process of the plant.The write access for the first servicing tool is included in thepredefined access rights in the field device and can thus be executedwithout limitation.

While a write accessing is being performed via the first servicing tool,a read request for a parameter is made to the field device F3 by thesecond servicing tool. The field device F3 again tests (as a function ofthe operational status, in which the field device F3 is running, and asa function of the profile information of the second servicing tool)whether the read request is included in the predefined access rights. Areading of parameters is here non-critical for the process. The readaccess is included in the predefined access rights and can be executedwithout limitation.

While performing the write accessing via the first servicing tool, theservice technician 6 would additionally like to perform a change of aparameter of the field device F3 via the handheld servicing device 8,and therewith, via the third servicing tool. After placement of a writerequest to the field device F3 by the third servicing tool, the fielddevice F3 tests (as a function of the operating state, in which thefield device F3 is running and as a function of the profile informationof the third servicing tool) whether the write request is included inthe predefined access rights. As is explained above, the field device F3is running in an operating state with write access blocked. The fielddevice F3 is thus blocked for an additional writing procedure. Theservice technician 6 is informed both via a display of the field deviceF3 as well as via a display of the handheld servicing device 8 that thefield device F3 is, at the moment, blocked by the first servicing tool,and that write access is not possible. As soon as the session with thefirst servicing tool is ended, the blocking in the field device F3 iscanceled. A corresponding report is displayed both on the display of thefield device F3, as well as on the display of the handheld servicingdevice 8.

The present invention is not limited to the example of an embodiment asexplained here with reference to FIG. 1. The present invention isespecially not only applicable in the case of sensors and actuatorsserving as the relevant field devices. Rather, the advantages set forthabove will also become evident in the case of remote I/Os, gateways andlinking devices. For example, a remote I/O, which is connected to afieldbus and which, via analog lines, is connected with one or moresimple field devices, can be operated according to the method of theinvention. Instead of the Profibus® bus system, another bus system, suchas, for example, a HART® bus system, a Foundation Fieldbus bus system,etc., can also be applied.

The invention claimed is:
 1. A method for operating a field device ofprocess automation technology, wherein the field device has stored in amemory, profile information for different servicing devices andassociated with the profile information is, in each case, anidentification of the corresponding servicing device, wherein the methodcomprises the steps of: connecting the field device for communicationwith at least one servicing device; and in case of a request by aservicing device for access to the field device the servicing devicetransmits its identification and the field device can access theassociated profile information via the received identification and as afunction of said profile information allows an accessing by theservicing device, thus access allowed by the field device depends on theparticular servicing device which places the access request, and on theoperating state, in which the field device is operated, where in: saidoperating states include an operating state with blocked or limitedaccess, in which the field device is operated, when a request for accessto the field device is placed by a servicing device and wherein saidoperating states of the field device, as a function of which anaccessing is allowed, include at least three of the following operatingstates: an “offline” operating state, in which the field device is notconnected in a plant of process automation technology; and “online”operating state, in which the field device is connected in a plant ofprocess automation; a “commission” operating state (“start-up” operatingstate), in which parameters of the field device are set beforeintegration of the field device into a process; a “non-commission”operating state (operating state before start-up), in which a fielddevice, which has not previously been in operation, is present; an“off-control” operating state, in which the field device is “online”,but is not, however, yet integrated into a process; an “on-control”operating state, in which the field device is “online” and integratedinto a process.
 2. The method as claimed in claim 1, wherein: dependingon the servicing device which places the access request and/or dependingon the operating state of the field device, access allowed by the fielddevice only includes a part of the parameters of the field device. 3.The method as claimed in claim 1, wherein: depending on the servicingdevice which places the access request and/or depending on the operatingstate of the field device, access allowed by the field device onlyincludes certain access types.
 4. The method as claimed in claim 1,wherein: in case of an access request, the at least one servicing devicetransmits an identification of the servicing tool to the field device.5. The method as claimed in claim 1, wherein: profile information forthe at least one servicing device is saved in the field device; theprofile information includes information regarding functions of therelevant servicing device with regard to an accessing of field devices;and the field device, in case of receiving an access request by aservicing device, accesses the profile information of the servicingdevice, and, as a function of this profile information, allows anaccessing.
 6. The method as claimed in claim 1, wherein: in the fielddevice, upon receiving an access request by a servicing device, accessby other servicing devices is blocked or enabled only to a limiteddegree.
 7. The method as claimed in claim 6, wherein: that the blockingor limitation of access to the field device can only be canceled by theservicing device which placed the access request, due to which accesswas blocked or limited.
 8. The method as claimed in claim 1, wherein:the field device, upon receiving an access request from a predeterminedservicing device, allows an accessing independently of whether an accessrequest was parallelly placed by another servicing device.
 9. The methodas claimed in claim 6, wherein: when an access is blocked or enabledonly to a limited degree, the field device gives a corresponding reportconcerning the blocking or limitation; wherein, in the report, anidentification is especially given of the servicing device, which placedthe access request, due to which access was blocked or limited.
 10. Themethod as claimed in claim 1, wherein: in case of an access requestinitiated by a person, this person must identify him/herself, and accessallowed by the field device depends on identity of this person.
 11. Afield device of process automation technology, which has stored in amemory, profile information for different servicing devices andassociated with the profile information is, in each case, anidentification of the corresponding servicing device, wherein the fielddevice includes a processor unit, adapted in such a manner, that, incase of a request by a servicing device for access to the field device,access to the field device allowed by the processor unit depends on theparticular servicing device, which places the access request, and on theoperating state, in which the field device is operated wherein: saidoperating states include an operating state with blocked or limitedaccess, in which the field device is operated when a request for accessto the field device is placed by a servicing device and wherein saidoperating states of the field device, as a function of which anaccessing is allowed, include at least three of following operatingstates: an “offline” operating state, in which the field device is notconnected in a plant of process automation technology; an “online”operating state, in which the field device is connected in a plant ofprocess automation technology; a “commission” operating state(“start-up” operating state), in which parameters of the field deviceare set before integration of the field device into a process; a“non-commission” operating state (operating state before start-up), inwhich a field device, which has not previously been in operation, ispresent; an “off-control” operating state, in which the field device is“online”, but is not, however, yet integrated into a process; an“on-control” operating state, in which the field device is “online” andintegrated into a process.